According to Model Press, the burger's croquette is made with snow crab and mushrooms and served with a tomato sauce and lettuce on Ciabatta bread. Note that McDonald's Japan is calling the sandwich a burger.

Crab croquettes (カニクリームコロッケ) are fairly common in Japan, so that in itself is not unusual. I'm a fan of them! That's why it's actually kind of cool to see a crab croquette burger at McDonald's.

So yes, it certainly seems like this meal could be good and is nowhere near a daunting as the snow crab burger that Wendy's offered in Japan a while back.